Multichannel catheter

ABSTRACT

This invention is a single, multichannel catheter useful for extracorporeal circulation of blood to a patient undergoing cardiovascular treatments or surgery. The catheter has three independent channels and an expandable balloon at one end of the catheter. The first channel is the largest and is of a size that allows for delivery of blood to a patient in an amount sufficient to maintain the patient&#39;s metabolism and perfusion throughout the treatment or surgery. A second channel, smaller than the first. is integrated into the wall of the first channel. and is suitable for delivering a biologically active fluid (e.g., for cardioplegia) to the heart and/or venting the left heart. A third channel, also smaller than the first, is integrated into the wall of the first channel, and suitable for delivering a fluid to the balloon for its expansion when positioned in the ascending aorta to occlude the flow of blood to the heart. Preferably, the first channel accounts for at least about  70 % of the total channel volume. The catheter provides an improved means of performing cardiovascular surgery on a patient using a cardiopulmonary machine for extacorporeal circulation of blood. The catheter is particularly useful for cardiac surgery. The catheter is particularly useful for cardiac surgery. The multichannel catheter is best prepared using an extrusion molding technique.

CROSS-REFERENCE

[0001] This is a continuation-in-part of provisional application U.S.Application No. 60/014,922, filed 10 April 1996.

FIELD OF THE INVENTION

[0002] This invention relates to a multichannel catheter for use inconjunction with cardiovascular examinations, treatments and surgery. Italso relates to methods for making and using such a catheter.

BACKGROUND OF THE INVENTION

[0003] To better understand the background and problems faced by thoseof skill in this area of technology it is useful to understand the basicworkings of the heart and circulatory system. The following discussionrefers to schematics of the heart shown in FIGS. 1 and 2.

[0004] The human heart is a muscular pump having four separate cavitiesand a series of valves allowing blood to pass in one direction only.Mammals, including humans, have a double circulatory system. Blood thathas released oxygen to the tissues (9 and 14) and has absorbed carbondioxide from them (venous blood) is returned to the heart through thesuperior and the inferior venae cavae (11 and 10). This blood enters theright auricle (3), whose contractions cause the blood to pass throughthe tricuspid valve (16) in the right ventricle (1). The contractions ofthe right ventricle pass the blood through the pulmonary semilunarvalves (17) and along the two pulmonary arteries (5) into the lungs (6).In the lungs, the blood is oxygenated and returns to the heart throughthe pulmonary veins (7) and thus enters the left auricle (4). Thischamber contracts and passes the blood through the bicuspid, or mitral,valve (15) into the left ventricle (2), whose contractions force theblood through the aortic semilunar valve (18) into the aorta (12 and13), which is the biggest artery of the body and to other parts of thebody through, i.a., the great arteries 8.

[0005] Thus the right side of the heart serves mainly to pumpdeoxygenated blood through the lungs, while the left side pumpsoxygenated blood throughout the rest of the body. This is represented asa flow schematic in FIG. 2, where similar numbers refer to similar partsof the heart. The heart varies the output by varying the volume of bloodadmitted into the ventricles each time the latter are filled and also byvarying the rate of contraction (faster or slower heartbeat). The leftside of the heart (left auricle and ventricle) has to circulate theblood through all parts of the body, except the lungs, and has thickerand more strongly muscular walls than the right side, which has toperform the pulmonary blood circulation only. For proper functioning,the left side and the right side must be accurately interadjusted, bothwith regard to the contraction rate of the respective chambers and withregard to the output of blood. When functional disorders of the heartoccur, it may be necessary to examine the heart to determine the problemand possibly perform surgery or provide treatment.

[0006] In performing examinations or treatments of a subject's heart, orperforming surgery on the heart, it is often necessary to reduce therate at which it normally beats or stop its beating completely. Thisallows a physician to observe, or operate on, the heart more easily.However, by reducing or stopping the heart rate (i.e. cardioplegia),blood will not be adequately circulated to the rest of the body. Thus,it is generally necessary to circulate the blood using some type ofextracorporeal blood circulating means that regularly circulatesoxygen-rich blood through the arteries, collects oxygen- depleted bloodreturning through the veins, enriches the oxygen-depleted blood withadditional oxygen, then again circulates the oxygen-rich blood.

[0007] The types of examinations, treatments and operations that requiresome degree of cardioplegia or drug delivery and extracorporeal bloodcirculation include open heart surgery and less-invasive heart surgeryto perform single or multiple coronary artery bypass operations, correctmalfunctioning valves, etc. Others include, but are not limited to,myocardial revascularization, balloon angioplasty, correction ofcongenital defects, surgery of the thoracic aorta and great vessels, andneurosurgical procedures.

[0008] The extracorporeal blood circulation generally requires the useof some type of heart-lung machine, i.e. a cardiopulmonary machine. Thishas the threefold function of keeping the replacement blood incirculation by means of a pumping system, of enriching with fresh oxygenthe blood of low oxygen content coming from the patient's body, andregulation of patient temperature. The system shown in FIG. 3diagrammatically describes the manner in which such a machine works.

[0009] The venous blood, before it enters the right auricle of the heartis diverted into plastic tubes (20), generally by gravity flow. Thetubes are positioned to receive the blood from the superior and inferiorvenae cavae (shown as 11 and 10 in FIG. 1). This blood, which hascirculated through the body and consequently has a low oxygen content iscollected in a reservoir (21). A blood pump (22) is used to pump theblood through a heat exchanger (23) and artificial lung (24). The heatexchanger (23) and artificial lung (24) may be one of several designs toregulate blood temperature and increase the oxygen content of the blood.Modern designs use advanced membrane technology to achieve theoxygenation, which is similar to the way red blood cells absorb oxygenfrom the human lung. The oxygenated blood then passes through a filter(25) and is returned to the patient. Losses of blood occurring duringthe course of the operation are compensated by an additional bloodreservoir (26). Collected blood is passed through a defoamer (27) and islikewise passed to the to the reservoir 21, heat exchanger (23) andartificial lung (24). Before starting the cardiopulmonary bypass machinethe extracorporeal circuit is filled with one or two liters of salinesolution.

[0010] In circulating the oxygenated blood to the body from filter 25,it can be pumped through a catheter 28 by inserting the catheter intothe aorta or one of its major branches and pumping the blood through thecatheter. However, when the heart is to be operated on, it must be freeof blood and sometimes the heart beat must be reduced or stoppedcompletely. Referring again to FIG. 1, blood is prevented from enteringthe heart by blocking the ascending aorta 12 near the semilunar valve 18while at the same time preventing blood from entering the right auricle3 by withdrawing blood through the superior vena cavae 11 and inferiorvena cavae and 10. Blocking the ascending aorta may be achieved byclamping or preferably by balloon blockage. At the same time that bloodis prevented from flowing through the heart, a cardioplegia solution isadministered locally to the heart to arrest the heart. Thus, there is aneed for a device that allows a heart specialist to locally administercardioplegia to the heart, block the flow of blood to the heart, whileat the same time circulating oxygenated blood to the patient's body,particularly through the great arteries (8 in FIG. 1), to ensure alllimbs and tissues remain undamaged during the heart examination oroperation.

[0011] Several devices are described in the literature to address theneed for an appropriate device. One example is disclosed in U.S. Pat.No. 5,312,344 issued 17 May 1994 to Grinfeld et al. This patentdescribes a multichannel catheter having at least three passageways, oneof which is used for blood circulation and another is used forcardioplegia transportation. The third is used to transport fluid to aninflatable balloon which is located at the distal end of the catheterand is used to block the ascending aorta. The channel for blood isdescribed as having outlets on the downstream side of the balloon toallow blood to be circulated to the body tissues. The design of thismultichannel catheter shows that either each passageway is a tubeencased in a cannula or the smaller passageways are located within thelarger passageway for cardioplegia solution or blood. Thus, the smallpassageways are not integral with the walls of the blood-carrying tube.Also, there is no teaching of the importance of the large volume neededfor the blood-carrying catheter.

[0012] Another example can be seen in U.S. Pat. No. 5,433,700 issuedJul. 18, 1995 to Peters. This patent describes a process for inducingcardioplegic arrest of a heart which comprises maintaining the patient'ssystemic circulation by peripheral cardiopulmonary bypass, occluding theascending aorta through a percutaneously placed arterial ballooncatheter, venting the left side of the heart, and introducing acardioplegia agent into the coronary circulation. As part of thedisclosure a multichannel catheter is disclosed which provides channelsfor the cardioplegia solution, a fluid transportation to inflate theballoon and a lumina for instrumentation. However, there is nodescription in the patent of a multichannel catheter which is designedto administer cardioplegia solution, inflate a balloon, and providecirculation of blood all using the same multichannel catheter. ThePeters process teaches the use of a separate catheter to deliveroxygenated blood to the body while a heart is stopped.

[0013] Another example of a device is found in U.S. Pat. No. 5,478,309issued Dec. 26, 1995 to Sweezer et al. This is a rather complex deviceand system of venous perfusion and arterial perfusion catheters for usein obtaining total cardiopulmonary bypass support and isolation of theheart during the performance of heart surgery. One of the multichannelcatheters described in the patent for delivering cardioplegia solutionto the heart while blocking the ascending aorta and circulating perfusedblood. This catheter requires a cannula having two passagewaystherethrough. In the first passageway another slidable cannula havingtwo passageways through it and having a passageways for guidewires arepositioned. These passageways are for delivering a fluid for inflatingthe balloon at the distal end of the catheter and cardioplegia solutionto the heart to stop its beating. The second passageway through thecannula used for transporting blood that has been oxygenated by thecardiopulmonary machine. However in this particular design no discussionof the need to maximize the flow of blood and minimize the damage to theblood components is discussed. Thus the volume of the two passageways isabout the same.

[0014] Another device is described in U.S. Pat. No. 5,458,574 issuedOct. 17, 1995 to Machold et al. It shows a multichannel catheter whichhas channels for fluid to blow up balloons for blocking the aorta, achannel for cardioplegia solution and a channel for instruments forexamining the heart. Nothing in the patent describes a multichannelcatheter of applicant's design.

[0015] Still another patent, U.S. Pat. No. 5,452,733 issued Sep. 26,1995 to Sterman et al. No details are given in that patent of the designof the catheter that might be used.

[0016] Still another patent application filed as PCT/US 94/09938 havinginternational publication No. WO95/08364 filed Sep. 1, 1994 in the nameof Evard et al. describes an endovascular system for arresting theheart. This too lacks any detailed description of a multichannelcatheter that could be used in the manner described in the instantapplication.

[0017] PCT International Application number PCT/U.S. Pat. No. 94/12986published as Publication No. W095/15192, filed Nov. 10, 1994 in the nameof Stevens et al. provides a description of a partitioning device thatis coupled to an arterial bypass cannula. The description provides forthe cannula to be introduced to the femoral artery where thepartitioning device has a balloon at the end of the flexible tube toblock the ascending aortic artery and allow blood to circulate through alumen.

[0018] While the above devices address in part the needs of the art, ithas been discovered that certain problems exist that must be furtheraddressed to maximize the efficiency of the device and cardiopulmonaryoperations. The first problem is ensuring maximum flow of blood throughthe device (which must be of a diameter sufficiently small to fit into apatient's femoral artery) so that the tissues receive enough nourishment(i.e. oxygen, etc.). We have found that by ensuring that (1) the channelfor blood is at least 70% of the available volume and (2) the channelfor blood is clear of an other tubes or obstructions, the blood flow ismaximized. Another problem is ensuring that the blood components are notinjured by excess flow rate and sheer stress in the circulation process.We have found that by providing strategically located blood outlets thatare preferably elongate in shape the sheer stress is reduced. Anotherproblem is ensuring the blood flow to the great arteries is maximized toavoid damage to the tissues, particularly the brain. We have foundtissue damage is avoided by ensuring the blood circulating outlets arelocated on the catheter such that when the catheter of this invention isin place, the outlets are located adjacent to the great artery openings.Finally we have found that by using extrusion molding techniques themultichannel catheter of this invention is prepared so that (1) theblood-carrying passageway is at least about 70% of the available volumeand (2) the other passages account for less than about 30% of theavailable volume and are integral with the wall of the blood-carryingpassageway, the blood flow problems are minimized.

Objects of the Invention

[0019] An object of this invention is to provide a unique multichannelcatheter having multiple uses.

[0020] Another object of this invention is to provide a uniquemultichannel catheter useful in examinations of and surgical operationson a mammal's heart.

[0021] Another object of this invention is to provide a uniquemultichannel catheter useful for efficiently delivering oxygenatedextracorporeal blood through a major channel of the catheter tosupplement or replace blood from the mammal's heart.

[0022] Another object of this invention is to provide a uniquemultichannel catheter that maximizes the rate of blood flow through thecatheter's blood passageway while minimizing the outside diameter of thecatheter.

[0023] Another object of this invention is to provide a uniquemultichannel catheter that reduces the sheer stress on the blood pumpedthrough the catheter's blood passageway for delivery to the mammal'sarterial system.

[0024] Another object of this invention is to provide a bloodcirculating catheter that provides improved peripheral circulation andperfusion.

[0025] Another object of this invention is to provide a process forpreparing a unique multichannel catheter by extrusion molding.

[0026] Another object of this invention is to provide an improvedprocess for performing surgery on a mammal's heart.

[0027] Another object of this invention is to provide a uniquemultichannel catheter that is useful in both open chest and leastinvasive heart surgery.

[0028] It is another object of this invention to provide improvements inthe management and treatment of coronary heart disease.

[0029] It is another object of this invention to provide for easypositioning of a unique multichannel catheter through insertion into amajor branch of the aorta such as the subclavian or femoral artery tolocate the distal end of the catheter in the ascending aorta of themammal and precise placement of the balloon.

SUMMARY OF THE INVENTION

[0030] One aspect of this invention is a single, multichannel catheteruseful for extracorporeal circulation of blood to a patient undergoingcardiovascular treatments or surgery. The catheter has three independentchannels and an expandable balloon at one end of the catheter. The firstchannel is the largest and is of a size that allows for delivery ofblood to a patient in an amount sufficient to maintain the patient'smetabolism and perfusion throughout the treatment or surgery. A secondchannel, smaller than the first, is integrated into. the wall of thefirst channel and is suitable for delivering cardioplegia fluid to theheart and/or venting the left heart. A third channel, also smaller thanthe first, is integrated into the wall of the first channel and suitablefor delivering a fluid to the balloon for its expansion when positionedin the ascending aorta to occlude the flow of blood to the heart.

[0031] Another aspect of this invention may be viewed as an improvedmethod of performing cardiovascular surgery on a patient using acardiopulmonary machine for extracorporeal circulation of blood. Theimprovement comprises using the catheter of this invention to deliverblood to the patient, provide cardioplegia fluid to the heart, occludethe flow of blood to the heart, and vent the heart if needed.

[0032] Another aspect of this invention is the multichannel catheterwherein the large first channel (i) extends substantially the length ofthe catheter, (ii) comprises at least about seventy percent of theavailable channel volume of the catheter, (iii) is defined by the wallof the catheter, and (iv) has its distal end in fluid communication withthe expandable balloon. The second channel (i) extends substantially thelength of the catheter parallel to said first channel but independentthereof, (ii) is integrated into the wall of the first channel, and(iii) is open at its distal end. The third channel extends substantiallythe length of the catheter parallel to the first and second channels butindependent thereof. The third channel comprises, in combination withthe second channel, not more than about thirty percent of the availablechannel volume of the catheter, is integrated into the wall of the firstchannel and spaced from the second channel, and is closed at its distalend. In the wall of the catheter near the distal end of the catheter andcommunicating with said first channel are a plurality of openings. Theballoon means is integrated into the distal end of the catheterdownstream from the first channel openings but upstream of the secondchannel distal opening and communicates with the third channel throughan opening in the wall of the catheter. The catheter is of a sizesuitable for insertion into a blood vessel of a mammal and is for use inconjunction with cardiovascular examinations and surgery. Preferably theplurality of openings communicating with the first channel are elongatewith the length of the openings being parallel to the length of thecatheter and the first channel is large enough to transport oxygenatedblood there through from the proximal end to the distal end.

[0033] Another aspect of this invention is a process of preparing theprecursor to the multichannel catheter described herein, which processcomprises

[0034] (A) Extrusion molding a catheter having distal and proximal endswherein the catheter comprises

[0035] (1) a central, first channel (a) extending substantially thelength of the catheter, (b) comprising at least about seventy percent ofthe available channel volume of the catheter, and (c) being defined bythe wall of the catheter;

[0036] (2) a second channel (a) extending substantially the length ofthe catheter parallel to said first channel but independent thereof and(b) being integrated into the wall of the first channel;

[0037] (3) a third channel (a) extending substantially the length ofsaid catheter parallel to the first and second channels but independentthereof, (b) comprising, in combination with the second channel, notmore than about thirty percent of the available channel volume of thecatheter, and (c) being integrated into the wall of the first channeland spaced from the second channel. Other steps are taken to completethe catheter, as discussed hereinafter.

[0038] Another aspect of this invention is a process for providingoxygen-rich blood to a subject’s arterial circulation and providingcardioplegia solution to the heart of the subject to arrest the heartand minimize damage to the heart. The process comprises

[0039] positioning the multichannel catheter, as described hereinbefore,in the ascending aorta;

[0040] providing a source of oxygen-rich blood to the proximal end ofthe first channel of the catheter;

[0041] providing a source of cardioplegia fluid to the proximal end ofthe second channel of the catheter;

[0042] providing a source of fluid for inflating the inflatable means tothe proximal end of the third channel of the catheter;

[0043] positioning the multichannel catheter within the subject's bloodcirculatory system such that (a) the distal end of said catheter ispositioned in the ascending aorta and the first channel openings arelocated proximate the great arteries, (b) the inflatable means islocated on the cephalid side of the aortic valve, and (c) the distal endof the second channel is located proximate the aortic valve anddownstream of the inflatable means;

[0044] inflating the inflatable means to block the flow of blood to theheart;

[0045] pumping cardioplegia solution into the heart to arrest thesubject's heart rate;

[0046] pumping oxygen-rich blood through said first channel out thefirst channel openings at rate sufficient to maintain the subject'smetabolism and perfusion;

[0047] performing a surgical operation on the heart as needed; and

[0048] maintaining circulatory support of said subject as needed.

[0049] Other aspects of the invention will be apparent to one of skillin the art upon further reading the following specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1 is a diagram of a mammal's heart and circulatory systemshowing the approximate configuration of the heart.

[0051]FIG. 2 is a schematic representative of how a mammalian heartworks without regard to its configuration.

[0052]FIG. 3 is a schematic representation of how a cardiopulmonarymachine works.

[0053]FIG. 4 is a longitudinal cross-section view of a multichannelcatheter of this invention showing the interrelationship between themajor portions of the invention.

[0054]FIG. 5A is a perpendicular cross-section taken along lines 5-5 ofthe longitudinal axis of the device of this invention shown in 4A.

[0055]FIG. 5B shows a closely related configuration taken along line 5-5of FIG. 4a.

[0056]FIG. 5C shows a slight modification of the cross-section takenalong the line of 5-5 of FIG. 4.

[0057]FIG. 6 shows a cross-section of the longitudinal axis of aslightly different configuration of the multichannel catheter of thisinvention.

[0058]FIG. 7 shows a perpendicular cross-section taken along lines 5-5of FIG. 4 and shows the size relationships between the various parts ofthe multi-channel catheter of this invention.

[0059]FIG. 8 is a perspective closeup of the distal end of the catheterof this invention showing an inflated balloon and elongate openings.

[0060]FIG. 9 is a side elevation closeup of the distal end of thecatheter of this invention showing an alternative design for theelongate openings.

[0061]FIG. 10 is a side elevation closeup of the distal end of thecatheter of this invention showing an alternative design of theopenings.

[0062]FIG. 11 shows a cardiopulmonary system using the catheter of thisinvention.

[0063]FIG. 12 shows positioning the balloon at the distal end of thecatheter in the ascending aortic by insertion through the aorta.

[0064]FIG. 13 shows positioning the balloon at the distal end of thecatheter in the ascending aorta by insertion through the aorta near thesubclavian artery.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS DESCRIPTION OFTHE CATHETER

[0065] Broadly, this invention is a multichannel catheter useful incardiovascular surgery, which allows a physician to

[0066] deliver extracorporeal blood to a patient undergoingcardiovascular surgery,

[0067] occlude the flow of blood at the ascending aorta,

[0068] deliver cardioplegia fluid to the heart and

[0069] vent the left heart.

[0070] The multichannel catheter is of a diameter size to be insertedinto the aorta or one of its major branches (e.g. a femoral artery) andused in open chest surgery or in less invasive surgery. Alternatively,the catheter is used in open chest surgery and inserted by cannulationat the aorta or through one of the great arteries, e.g., thebrachiocephalic artery. The design of the blood flow configuration willdepend on where and how the catheter is to be inserted, as discussedhereinafter.

[0071] In general, the multichannel catheter of this invention comprisesat least 3 passageways,-with a large, central passageway to maximize theflow of oxygenated blood from a cardiopulmonary machine. An importantaspect of this invention is to maximize the flow of blood through thelarge channel while minimizing the outside diameter of the catheter andthus provide adequate systemic extracorporeal blood flow for the vastmajority of patients in which the catheter is used. Of the availablepassage space in the catheter of this invention at least about 70% isallocated to this large passageway to maximize the flow. Preferablyabout 80% and more preferably about 90% of the available passagewayvolume, is used for the flow of perfused blood to the arterial side of apatient in need of supplementary, extracorporeal blood circulation. Theother channels, at least two, comprise the remainder of the availablevolume (i.e., about 10%- 30%) with each channel integrated into the wallof the large central passageway. Generally, the available volume isdetermined by calculating the area of a cross-section of eachlongitudinal passageway and multiplying by the length. Since the lengthis about the same in each case, the relative volume for each channelwill be directly proportional to the cross-sectional area of eachpassageway.

[0072] More specifically, the multichannel catheter has distal andproximal ends and comprises a large central, first channel, i.e., apassageway or lumen. This channel extends substantially the length ofthe catheter, comprises at least about seventy percent of the availableinternal channel volume of the catheter, and is closed at its distalend, but has certain outflow openings for extracorporeal blow flow, asdiscussed in greater detail hereinafter. The catheter has at leastsecond and third channels, each of which extends substantially thelength of the catheter, parallel to said first channel but independentthereof. Together, these additional channels comprise not more thanabout thirty percent of the available internal channel volume of thecatheter and are integrated into the wall of the first channel. Thesecond channel (generally the larger of the two smaller channels) isopen at its distal end, while the third channel's distal end is incommunication with an inflatable means. The catheter further has aplurality of openings near the distal end of said catheter communicatingwith said first channel and an inflatable means, i.e., a balloon,integrated into the distal end of the catheter between the first channelblood outflow openings and said second channel's distal opening. Theopenings are said to be “upstream” of the balloon, while the distalopening of the second channel are said to be “downstream” of theballoon. The interior of the inflatable means communicates with thedistal end of the third channel through an opening in the wall of thecatheter. The catheter is made of physiologically acceptable materialand is of a size suitable for insertion into a blood vessel of a mammal,particularly a human. Preferably, at least some and preferably themajority of the plurality of openings communicating with the firstchannel are elongate in shape with the length of the openings beingsubstantially parallel to the length of the catheter.

[0073] Turning now to FIG. 4, one can see a detailed representation ofthe catheter of this invention which is a cross-sectional view of thelength of the catheter. The catheter is shown generally as 30 having aproximal end 31 and a distal end 33. The large first channel 34 isdefined by the wall 32 of the catheter. The second channel 36 and thethird channel 38 are shown as being integrated into the wall of thefirst large channel. The second and third channels are integrated withthe wall 32 of the first channel 34 and are shown as having an interiorwall portion 41 defining the smaller second and third channels.

[0074] Toward the distal end 33 of the catheter 30 are located openings40 that are outlet ports for the fluid passing through the channel 34.In use, that fluid will be blood that is circulated to the arterial sideof a patient in need of such extra-corporeal circulation. As will bediscussed in greater detail, hereinafter, the catheter of this inventionis preferably designed to be inserted into a femoral artery of a humanpatient and advanced sufficiently so that the distal end is positionedin the ascending aorta. Thus, the catheter must be flexible enough toreadily bend at its distal end as shown in FIG. 10, but it must also bedesigned to minimize kinking to avoid reduced fluid flow through thepassageways 34, 36 and 38 in FIG. 4. The openings 40 communicating withchannel 34 are located on the proximal side (i.e. upstream) of theinflatable means 42 (also referred to as the “balloon”) so that bloodflows out of channel 34 near the great arteries. While some of theopenings may be adjacent the balloon 42, preferably within about an inchof the proximal edge 44 of balloon 42, the openings 40 are located suchthat they do not contribute to kinking of the catheter as it passes theaortic arch. Thus the openings 40 are located in the distal portion ofthe catheter so that when the catheter is positioned as shown in FIG. 11the openings are in a region of the catheter that is relativelystraight. A few of the openings may be located immediately adjacent theproximal side of the balloon 42 (e.g., within about an inch of theproximal edge 44 of the balloon 42), while the majority will be proximalto the great arteries.

[0075] Alternatively if the catheter is used in open chest surgery, itcan be inserted through the aortic arch as shown in FIG. 12 or throughthe brachiocephalic artery 102 or one of its branches. In FIG. 12, thesame numerals are used in describing the catheter of this invention asare used in FIG. 4. Referring now to FIG. 12, the aorta is generallyshown as 100 with the ascending aorta 101 and the great arteries shownas 102 (brachiocephalic), 103 (carotid), and 104 (subclavian). Inopen-chest cardiovascular surgery, the catheter 30 is inserted at theascending aorta 101 to position balloon 42 snugly against the walls ofthe ascending aorta 101. In this case, because the catheter 30 does notflex around the aortic arch 105, there is not as much stress on thedistal end 33 of catheter 30 and less likelihood of kinking. Thusnumerous openings 40 may be located closer to balloon 42 as to insurethe flow of blood to the aorta. The same is true of cannulation throughone of the great arteries such as the brachiocephalic artery 102 or oneof its branches. Another region of insertion may be near the subclavianartery 104 through the aorta as shown in FIG. 13.

[0076] Whatever the insertion point of the catheter is, it is importantthat the total outflow capacity of the outlet ports 40 is greater thanthe inflow capacity of the blood flowing into the catheter. This willmean that total collective cross-sectional area of openings 40 willexceed the total cross-sectional area of channel 34. Thus, to calculatethe collective cross-sectional area of openings 40, one determines thearea of each opening and adds the area of each opening. Preferably thetotal area (i.e. outflow capacity) of the openings will exceed thecross-sectional area (i.e. inflow capacity) of channel 34 by at least afactor of 1.2. Having a factor of greater than about 2 is even morepreferable. For example, if the radius of channel 34 is 2.5 mm, thecross-sectional area is 19.6 (2.5×2.5×3.14=19.6) and the totalcross-sectional area of the openings 40 will be at least 23.6(1.2×19.6=23.6), more preferably 39.2 (2×19.6=39.2). Preferably, eachopening has a cross-sectional area of about 340mm2, preferably about 5to about 20mm². The total number of openings may be as few as 3 largeopenings up to about 20 openings of various shapes.

[0077] While-the shape of the openings 40 may be of any appropriateshape for the outflow of blood, it is preferable that some, generally amajority of the openings are elongate in shape. While the openings maybe positioned in any configuration at the distal end of the catheter,for example, the longitudinal axis of the elongate openings may bepositioned substantially parallel to the length of the catheter or at aslight angle such that it forms a helical design or the length could beperpendicular to the length of the catheter. However, it is preferredthat the elongate openings have the length of the opening substantiallyparallel to the length of the catheter. The number of openings that canbe present may vary from 3 to 20 or more but must be placed in a mannerthat the structural integrity of the catheter is maintained. By havingelongate openings instead of circular openings the sheer stress on theblood is reduced by allowing the blood to flow out of the outlets moreeasily. In addition to the elongate openings located in the distalregion of the catheter other openings may be located further upstream ofthe elongate openings 40. Further designs may be seen in FIGS. 8, 9 and10. The design of the openings 40 may generally be that of an oval, arectangle, a trapezoid or some similar elongated design. In general,they will be approximately one cm to about four cm, preferably about 2.5cm long with a width at the broadest portion of the opening no more thanabout 5 mm. The openings 40 are positioned at the distal end of thecatheter so that when the catheter is positioned with the balloon 42 inthe ascending aorta, the openings are adjacent the great arteries sothat blood can flow more freely to the great arteries to ensure thenecessary oxygenation of tissues (i.e. perfusion) for the rest of thebody. By having a majority of (e.g., oval) openings and ensuring theoutflow capacity exceeds the inflow capacity the sheer stress on theblood passing through the first channel 34 will be significantlyreduced. By having the elongate openings at the distal end andmaximizing the size of channel 34, the flow rate through the largechannel 34 may be up to six liters (L) per minute without having adverseaffect on the blood due to too much shear stress on the red cells,platelets or white cells. Having the elongate openings and properoutflow capacity also reduces the pressure drop between the proximal endwhere the catheter is attached to the cardiopulmonary machine and theexit at the openings 40. Generally, the pressure drop will be under 300millimeters of mercury and preferably under 200 millimeters of mercury.The pressure drop can be further reduced by having additional holestowards the proximal end of the catheter but somewhere between themidpoint of the catheter and the distal end. This design is seen in FIG.10. As discussed, before the openings 40 will be positioned andconstructed to minimize the chance of kinking when the catheter passesover the curve of the aortic arch and generally will be sufficientlyproximal of the balloon 42 with the largest cross-section of openings tobe positioned in a section of the catheter that remains straight. While,a few (e.g., 2-4) small openings may be placed within about 2.5 cmproximal of the balloon 42, the majority are about 7.5 cm to about 30 cmon the proximal side (i.e., upstream) of the balloon, depending on thecatheter sizing for the patient.

[0078] In general, the maximum length of the multichannel catheter ofthis invention will be that length necessary to insert the catheter intothe femoral artery of the patient and moving it up the artery to placethe distal end having the balloon within the ascending aorta. Dependingon the size of the patient, whether a child or an adult, the length maybe from about 40 centimeters up to about 100 centimeters or more.Generally, the range will be about sixty to about one hundredcentimeters with about eighty-five centimeters being an average lengthsuitable for most people. The length will be significantly less whenused in open-chest surgery with aortic insertion or brachiocephaliccannulation.

[0079] The outside diameter of the multichannel catheter of thisinvention will be such that it can be inserted and moved through thefemoral artery of the patient and located in the ascending aorta asdiscussed above. Generally, this will have an outside diameter (OD) ofno more than about 30 French, preferably of about 18 to 24 French withabout 20 to 22 French outside diameter fitting most patients. The Frenchscale is a scale used for denoting the size of catheters or othertubular instruments, with each unit being roughly equivalent to 0.33millimeters (mm) in diameter. For example, 18 French indicates adiameter of about 6 millimeters while 20 French would indicate adiameter of about 6.6 millimeters. The thickness of the wall 32 may bebetween about 0.2 mm to about 1.0 mm. Thus, the inside diameter ofchannel 34 will generally not exceed about 28.2 French, and may varyfrom about 14.8-22.5 French.

[0080] By using the multichannel catheter of this invention, which isdesigned to maximize the flow of blood within the large channel whileminimizing the outside diameter of the catheter, the peripheral flow ofblood to the extremities, i.e., the arms and legs is significantlyimproved over any known commercial catheter designs. This is thought tobe due not only to the improved blood flow through the catheter and outthe openings, but also to the smaller outside diameter of the catheterand flow of blood back down the femoral artery around the catheter.

[0081] In some cases, it may be preferable to provide the multichannelcatheter of this invention with a distal end that has a slight“preshaped” region designed into it. The preshaped region is designed tocorrelate to the aortic arch. In inserting the catheter the preshapedregion is maintained in a relatively straight condition by using astylet, i.e., a stiff plastic support mechanism positioned in channel34. This can be used in conjunction with a guide wire positioned inchannel 36. When the distal end of the catheter reaches the curve of theaortic arch, the catheter continues to be advanced via the femoralartery, but the stylet is slowly withdrawn allowing the precurved regionto bend around the aortic arch to have the balloon then located past thebrachiocephalic artery but before the coronary ostia.

[0082] As shown in the FIG. 4, at the distal end of the catheter of thisinvention there is located a inflatable means 42 which in general is aballoon that is attached to the distal end of the catheter. The interiorof the inflatable means is in fluid communication with the third channel38 so that the balloon can be inflated or deflated by transporting fluidthrough the channel to the balloon to inflate it or sucking the fluidout to deflate the balloon. The design of the balloon may be any designknown in the art, such as that shown in U.S. Pat. No. 5,423,745;5,516,336; 5,487,730; and 5,411,479, the pertinent parts of which areincorporated by reference. Other useful balloon components arecommercially available to one of ordinary skill. While one balloon isshown in FIGS. 4 and 8-13 multiple balloons could be used, e.g., two.However, for ease of use and preparation, one balloon is preferred. Itis also preferred that the distance between the proximal edge 44 of theballoon and the distal side 45 be such that the surface contact with theinterior wall of the ascending aorta wall be maximized. This helpsensure a tight seal to prevent leakage. This distance between 44 and 45may be from about 20 mm to about 50 mm, preferably about 30 mm to about40 mm.

[0083] The second channel 36 is designed to introduce a cardioplegiasolution, to evacuate fluid (i.e., vent the left ventricle), or to carrya guidewire or various types of probes or for treating the heart. Thus,it has at least one opening 37 at the distal end 33 of catheter 30downstream of balloon 42. This allows a cardioplegia solution or theappropriate fiberoptic cable to be inserted into the channel and movedthrough the channel out exit 37. It also allows for a negative pressureto be applied to vent the left ventricle of the heart.

[0084] In a preferred mode of operation, the catheter of this inventionis inserted percutaneously or by cutdown into the femoral artery of apatient and is threaded through the femoral artery to the ascendingaorta to be positioned there. Occasionally, it may be necessary tosupplement the flow of a patient's heart if it has been weakened, andthis can be done by flowing oxygenated blood through the centralpassageway 34 out the outlets 40 to the great arteries and otherarteries in the arterial system. If an operation is to be performed onthe heart, which requires arrest of the heart, the catheter ispositioned appropriately, the balloon is inflated to block the flow ofblood into the heart from outflow openings 40. Cardioplegia solution isadministered through channel 36 out opening 37 to arrest the heart andblood is circulated through channel 34 out openings 40 to maintaincirculation of oxygenated blood in the patient during the operation.

[0085] Turning now to FIGS. 5A through 5C and FIG. 6, one can see across-sectional view taken along lines 5-5 in FIG. 4. In these figures,it can be seen that the large central passageway 34 is defined by thewall 32 of the overall catheter and that the channels 36 and 38 areintegrated into the wall 32. They may be integrated so that they arepositioned more interiorly as shown in FIG. 5A or more exteriorly asshown in FIG. 5B with cross-sectional diameters that are essentially acircle. On the other hand, in FIG. 5C, the cross-sectional of channels36 and 38 may be elongated or oval. While the relative volumes of thetwo are shown to be about equal, the total volume of flow available forall passageways 34, 36 and 38 is divided as follows. The amount of fluidflowing through passageway 34 will be at least about seventy percent ormore (e.g., up to about 90%) in order to achieve the advantages of thisinvention with the flow through passageways 36 and 38 being theremaining thirty percent or less (i.e., down to about 10%). In general,there will need to be less volume in the channel for communicating withthe balloon than in the channel that is available for the cardioplegiaor the fiberoptic instruments or cable. While generally, it ispreferable to have the channels 36 and 38 opposed one hundred eightydegrees from each other as shown in FIGS. 5A to 5C, it may be possibleto have them adjacent as shown in FIG. 6. Having them adjacent makes thepreparation a bit more difficult than having them opposed as in FIGS.5A, 5B and 5C.

[0086] The ratio of the total volume of the cardioplegia channel 36 tothe balloon inflating channel 38 will vary from about 1:1 to about 4:1.So, for a multichannel catheter in which about 70% of the totalavailable volume is provided for the channel 34 and about 30% of thetotal available volume is provided for channels 36 and 38, channel 36will account for about 15% to about 24% with channel 38 accounting forabout 15% to about 6%. Alternatively if channels 36 and 38 collectivelyaccount for about 10% of the total available volume then channel 36 willhave about 5% to about 8% while channel 38 will have about 5% to about2%.

[0087] By referring to FIG. 7, one can see the relative proportions ofthe three channels of the multi-channel catheter of this invention. Inthe Figure the abbreviations have the following meanings:

[0088] ID—inner diameter

[0089] OD—outside diameter

[0090] IWT—inner wall thickness

[0091] OWT—outer wall thickness

[0092] Summarizing the dimensions, they are as follows:

[0093] OD 32: 16 -30 French (5.3-9.9mm)

[0094] ID 32: 14.8 -28.2 French (4.7-9.3mm)

[0095] OWT 32: .6 - 1.0 French (.2-0.3=m)

[0096] IWT 41: .6 - 1.0 French (.2-0.3mm)

[0097] ID 38: .6 - 1.0 French (.2-0.3nm)

[0098] ID 36: .6 - 4.0 French (.2-1.3mm)

[0099] The catheter of this invention is able to handle a blood flowrate through the central channel 34 of about one-half up to about 6liters per minute with the proper sizing and design. Generally, a flowof about 5 liters per minute is sufficient to handle the vast majorityof circulatory needs required by patients having heart surgeryperformed. On the other hand, the flow of cardioplegia solution ordrug-containing solution through channel 36 is-generally about 100 toabout 300 cubic centimeters (0.1 - 0.3 liters) per minute. The ballooninflation channel 38, which is generally smaller than channel 36, willbe of a size sufficient to carry balloon-inflating fluid, e.g., saline,to the balloon. The volume of the balloon is generally about 40cc toabout 100cc, generally about 60cc. Thus, channel 38 is of a sizesufficient to carry that volume over a short period of time, i.e., lessthan a minute and generally less than about 10 seconds. The volume ofthe balloon will be greater if the distal end of the multichannelcatheter is tapered in the region covered by the balloon.

[0100] In general, the catheter of this invention will need to beflexible enough to easily be inserted up through the femoral artery tobe positioned in the ascending aorta. The flexibility needs to besufficient so that the catheter can bend but will not kink at bodytemperature. In general, this flexibility is measured by Durometer andwill be somewhere in the 55 to 65 range. Generally, we will have aDurometer reading of about 60. It is preferable that the distal endwhere the balloon is located is somewhat stiffer than the rest of thecatheter. This helps to ensure the positioning of the balloon in theascending aorta to ensure that it does not get displaced during theoperation.

[0101] Turning now to FIGS. 8-10, one sees a closeup of the distal end33 of catheter. It should be understood that the figures arerepresentative, but are not necessarily drawn to scale. This is anexternal view that show the elongate openings 40 and the balloon 42 inits inflated form, although not fully inflated. In general, the balloonis preferably of an oblong shape as shown in FIG. 8. This maximizes thesurface contact with the ascending aorta wall and minimizes the stresson the vessel wall by dispersing the pressure over a greater area. Bymaximizing the surface contact, the position is maintained to a greaterextent. While the surface of the balloon may be smooth, as shown in FIG.10, it preferably has a design on it that provides additional frictionbetween the balloon surface and the internal surface of the aortic arch.Thus the balloon surface may have either depressions, as shown in FIG.8, or ridges, as shown in FIG. 9, in a design that helps maintain theballoon in position. It is preferable to have on the surface of theballoon certain ridges or bumps indicated in FIG. 9 as 43 to provideadditional friction for maintaining the position of the balloon in placeand minimizing the disruption of plaque that may be present. Generally,the volume of the balloon will be about 30 to about 100 cubiccentimeters, preferably about 60cc. The length of the balloon from itsproximal end 44 to its distal end 45 will generally be about 2.5cm toabout 7.5cm with about 4cm being optimal. It will need to expandsufficiently to block the ascending aorta completely so that blood doesnot get to the arrested heart from the cardiopulmonary machine.

[0102] In performing open heart or least invasive cardiac surgery,generally, it is necessary to do an angiogram by placing an angiogramcatheter up the femoral artery and positioning it in the ascendingaorta. Based on the length of the angiogram catheter balloon placementposition can be determined, the multi-channel catheter of this inventionhas markings indicating its length measured from the distal end tovarious distances near the proximal end so that the physician knowsexactly how far to insert the catheter of this invention. Having thatinformation indicated on the catheter makes it easier for the physicianto do the insertion and also reduces the need to use fluoroscopy toproperly insert the catheter. On the other hand, if a angiogram cathetermeasurement is not done before inserting the catheter of this invention,an ultrasound probe may be used to position the catheter of thisinvention where the catheter of this invention carries a detectable beamon the tip of the catheter. Alternative methods may be employed forpositioning the catheter, such as guidance by fluoroscopy orechocardiography, fiberoptic visualization through the catheter,magnetic or electronic guidance, or other means of insuring properplacement.

[0103] The material which is used to manufacture the multichannelcatheter of this invention may be any material that is physiologicallyacceptable, that is it is made of a material that will not have anadverse effect on the patient when used in the manner in which it isintended. Generally this will require the use of biocompatible material(i.e. the body will not react with it) for preparing the catheter ofthis invention. In addition, the material that is used must possesssufficient stability and flexibility to permit its use in accordancewith the process of the invention. Various biocompatible polymers may beused. A polymer that is particularly valuable for preparing the catheterof this invention is polyvinyl chloride (PVC) blood tubing, that hasbeen plasticized. Preferably the plasticizer which is used in the PVC istrioctyl trimellitate (TOTM) while the standard plasticizer di-(2-ethylhexyl) phthalate (DEHP). TOTM plasticizer is less extractable than DEHPand produces a better blood response. Suitable PVC resin is availablefrom Dow Chemical Corp., Midland, Mich., or Polymer Technology Group(P.T.G.) Inc., Emeryville, Calif. Another polymer that is useful forpreparing the multichannel catheter of this invention is medical gradepolyurethane. Other polymers may be prepared based on a family ofpolysiloxane-containing copolymers termed surface modified additions(SMAs). These copolymers may be blended with the base polymer beforeprocessing or coated on the blood contacting surface. When blended withthe base polymer the SMA will migrate to the polymer surface resultingin a high concentration of the SMA of that surface, which has feweradverse reactions with the blood that contacts it. When coated, devicesurfaces are pure SMA. High surface concentration of the SMA areresponsible for the improved biocompatibility of extracorporeal circuitcomponents. Plasticized PVC is particularly useful as the base polymer.A further description of these polymers is given in article entitled“Surface Modifying Additives for Improved Device-Blood Compatibility”from ASAR Journal1994 M619-M624 by Chi-Chun Tsai et al. The article isincorporated herein by reference. Such polymers are available fromP.T.G. Corp.

[0104] Other useful polymers include polyurethane-urea biomaterials thatare segmented polyurethane (SPU) some of which have surface-modifyingend groups (SMES) covalently bonded to the base polymer. These aredescribed by Ward, et al. in an article entitled “Development of a NewFamily of Polyurethaneurea Biomaterials” in Proceedings From the EighthCimtec—Forum on New Materials Topical Symposium VIII, Materials inClinical Applications, Florence, Italy, July, 1994. See also U.S. patentapplication Ser. No. 08/221,666, which is incorporated herein byreference.

[0105] Sometime the blood interacts with artificial surfaces of polymersin such a way that the blood coagulates on the surface creating thrombi.These thrombi can block the catheter or blood vessels, preventing theblood from flowing and causing oxygen depletion and nutrient starvationof the tissues. Thus the surface of the polymeric material used for themultichannel catheter of this invention should not give rise to thrombusformation. An anti-thrombotic agent can be used to prevent the clotsfrom forming. Some of the blood polymer interactions are discussed inarticle entitled “Biomaterials in Cardiopulmonary Bypass” found inPerfusion1994; 9:3-10 by James M. Courtney et al.

[0106] Polymer modifications that permit an improvement in bloodcompatibility while maintaining acceptable levels of other fundamentalproperties include the treatment of surfaces with protein, theattachment of anti-thrombotic agents and the preparation ofbiomembrane-mimetic surfaces. The preferred anti-thrombotic agent is theanti-coagulant heparin which can be attached ionically or covalently.Preferably it is attached covalently.

[0107] An additional factor to consider in preparing the catheter ofthis invention is the relative roughness of the blood-contactingsurface. Excess surface roughness has deleterious effects on blood flowthrough the catheter and should be avoided.

[0108] Another article that discusses the factors relating tocompatibility of surfaces contacting blood is entitled “State-of-the-ArtApproaches for Blood Compatibility” from Proceedings of the AmericanAcademy of Cardiovascular Perfusion Vol. 13, January 1992, pages 130-132by Marc E. Voorhees, et al.

[0109] Use of the Catheter of This Invention

[0110] The catheter of this invention may be used in several differentways. For a condition in a patient that needs supplementaryextracorporeal blood circulation because of insufficient circulationfrom his or her own heart, the catheter may be introduced via a femoralartery, positioned as appropriate and attached to a cardiopulmonarybypass machine to circulate blood through the large central channel 34and out openings 40. When appropriately positioned with the distal endof the catheter in the ascending aorta, a fine fiber optic cable may bethreaded through second channel 36 to examine the aortic area of theheart. If it is determined that a heart operation is necessary, theballoon may be inflated through channel 38 to block the ascending aorta,cardioplegia solution may be administered through channel 36 to arrestthe heart, and oxygenated blood from a cardiopulmonary machine is pumpedthrough channel 34 and openings 40 into the arterial pathway of thepatient's circulatory system. Thus, the device of this invention may beused in cardiovascular surgery in general or various heart examinationsor treatments of artery and valvular disease. Cardiovascular surgery ismeant to include surgery to the heart or to the vascular system of apatient. The catheter is particularly useful in cardiac surgery, whetheropen chest surgery or minimally invasive heart surgery. Such surgery mayinclude, but are not limited to, the following:

[0111] 1. Coronary artery revascularization such as:

[0112] (a) transluminated balloon angioplasty, intracoronary stenting ortreatment with atherectomy by mechanical means or laser into thecoronary arteries via one lumen of the catheter or

[0113] (b) surgical mobilization of one or both of the mammary arterieswith revascularization achieved by distal anastomoses of the internalmammary arteries to coronary arteries via a small thoracotomy.

[0114] 2. Any atrial or ventricular septal defect repair such as by

[0115] (a) “closed” cardioscopic closure or

[0116] (b) closure as in “open” procedure via a thoracotomy or otherlimited access incision.

[0117] 3. Sinus venosus defect repair similar to above.

[0118] 4. Infundibular stenosis relief by cardioscopic techniques.

[0119] 5. Pulmonary valvular stenosis relief by cardioscopic techniques.

[0120] 6. Mitral valve surgery via thoracotomy.

[0121] 7. Aortic stenosis relief by the introduction of instrumentationvia a lumen in the aortic catheter into the aortic root.

[0122] 8. Left ventricular aneurysm repair via a small left anteriorthoracotomy.

[0123] A significant advantage of the unique multichannel catheter ofthis invention is its ability to be adapted to be used in accordancewith the needs of a patient. For example, a patient with symptomaticcoronary artery disease undergoes a diagnostic evaluation to determinethe type of treatment that best suits that patient's condition. As aresult of the evaluation, the physician may recommend surgicaltreatment, interventional cardiology treatment or some alternativetreatment. Interventional treatment may include percutaneoustransluminal coronary angioplasty, atherectomy or the use of a stent tokeep the vessels open. Alternative treatment may include the use of alaser or myoplasty.

[0124] If additional treatment is recommended, the multichannel catheterof this invention is particularly valuable in the further evaluation todetermine the condition of the patient,the type of treatment recommendedand the type of drugs that might be useful to administer to the patient.Thus, in using the multichannel catheter of this invention, the catheteris inserted into a femoral artery by percutaneous puncture or directcut-dow. The distal end of the catheter, which carries the balloon, isinserted first and moved through the femoral artery to be positioned inthe ascending aorta as discussed in more detail hereinafter. Initially,the physician performing the work may wish to introduce instrumentsthrough the channel (36 in FIG. 4) or other probes to allow observationor measurement of the internal condition of the artery, aortic archand/or aortic semilunar valve. A cardioscope, an electrophysiologyprobe, a transmyocardial revascularization probe, a radiation probe, orthe like may also be inserted through channel 36. Once observations aremade concerning the condition of the heart and associated arteries, thephysician can then take additional steps. For example, it may bedesirable to administer a biologically active fluid directly to theheart or aorta using an appropriate liquid composition containing anactive entity appropriate for the patient's condition. The activeentities in such a biologically active fluid include drugs (particularlythose having cardiovascular effect) that are pharmaceutically acceptablesmall organic molecules, small polypeptide molecules, larger polypeptidemolecules, and even a DNA or RNA that may be useful for gene therapy.Examples of useful molecules include those useful as antianginals (e.g.,organic nitrates, calcium channel blockers, β-adrenergic antagonists)antihypertensive, antiarrhythmics, antihyperlipoproteinemias, myocardialcontractile enhancers, anti-atherosclerotic agents, and the like. Suchfluids especially for cardioplegia can best be delivered through channel36 in FIG. 4, but alternatively can be delivered in the fluid used toinflate balloon 42 through channel 38 in FIG. 4. In the latter case, thematerial used for the balloon would be semipermeable to allow the drugto diffuse through the balloon membrane. A drug having lipid-dissolvingcharacteristics can be delivered through the balloon membrane.Alternatively, it may be useful to deliver such an active agent byadding it to the cardiopulmonary machine reservoir.

[0125] Once the catheter is in place, and observations regarding theinternal conditions have been made, the physician then can move on tothe next steps. For example, least invasive surgery, as discussed inU.S. Pat. No. 5,452,733, may be performed on a beating heart with noinitial cardiopulmonary support, i.e., no blood would flow through thewould continue to function. If at any time, the physician would decidethat cardiopulmonary support would be needed, supplemental blood flowfrom a cardiopulmonary (heart/lung) machine could be started and workcould be continued with a beating heart or a fibrillating heart. Once adecision is made to completely arrest the heart, cardioplegia solutionis delivered to the heart through the channel 36 after balloon 42 isinflated to block the flow of blood to the heart from thecardiopulmonary machine. As described, the multichannel catheter of theinvention can be used in least invasive surgical procedures as well asopen chest surgery.

[0126] The multichannel catheter of this invention is particularlyuseful in performing heart surgery where the heart is arrested using acardioplegic solution and blood is circulated to the patient via acardiopulmonary bypass machine. In this case oxygenated blood iscirculated through the large channel of the catheter of this invention.The introduction of negative pressure on the venous drainage system maybe used to enhance venous drainage and reduce the need to vent the rightside of the heart. Generally, the negative pressure may be maintained atthe vena cavae regions (superior and inferior) using a centrifugal pumpattached to a standard femoral venous cannula. A system for performingsuch a process is depicted in FIG. 11.

[0127] In general, the process for performing surgery on a mammal'sheart comprises a sequence of steps. A single femoral access cannula isinserted into the mammal's femoral vein to position it so the distalopen end of the cannula is adjacent the vena cava region of the mammal'sheart and the proximal end of the cannula is attached to acardiopulmonary bypass machine through a centrifugal pump wherein thecardiopulmonary bypass machine comprises a blood oxygenation meansfluidly connected to the centrifugal pump. At about the same time amultichannel catheter of this invention is inserted into a femoralartery.

[0128] The multichannel catheter is positioned within the subject'sblood circulatory system such that the distal end of said catheter ispositioned in the ascending aorta such that the first channel openingsare located near the great arteries, the inflatable means is located onthe cephalid side of the aortic valve and the distal end of the secondchannel is located proximate the aortic valve and downstream of theinflatable means.

[0129] Next, a source of oxygenated blood from the cardiopulmonarymachine is connected to the proximal end of said first channel of thecatheter and a source of cardioplegia fluid is connected to the proximalend of said second channel. A source of fluid is connected for inflatingsaid inflatable means to the proximal end of said third channel and theinflatable means is inflated to block the flow of blood to the heart.

[0130] Cardioplegia solution is pumped into the heart to arrest themammal's heart and oxygen-rich blood is pumped through said firstchannel out the first channel openings upstream of the balloon at ratesufficient to maintain the subject's metabolism and perfusion while atthe same time oxygen-depleted blood is removed from the mammal's venacavae regions through the femoral vein cannula by applying a negativepressure using the centrifugal pump. The physician can then perform asurgical operation on the heart as needed and said subject is maintainedas needed.

[0131] Referring to FIG. 11, the femoral vein is accessed percutaneouslyor by cut down using the appropriate size standard femoral accesscannula 50 (such as an Research Medical Inc. #TF-030-050). This cannulaconducts de-oxygenated venous blood from the vena cava 51 to PVC tubing52 (e.g. 0.5 inch inner diameter). This tubing is attached to thenegative pressure (inlet) port 53 of a centrifugal pumping device 54(such as the St. Jude Medical #2100CP); the positive pressure (outlet)port 55 of the centrifugal pumping device is connected via tubing 56(0.5 inch ID PVC) to a venous reservoir system 57 (such as the COBECardiovascular, Inc. VRB 1800). This configuration pulls blood from thevena cava 51 to the venous reservoir 57. Utilization of negativepressure in this manner to provide venous blood return eliminates theneed to “vent” or empty the right heart. By using a centrifugal pumpthat reaches about -20 to about -50 mm of mercury (mm Hg), a sufficientnegative pressure is maintained. The use of a closed reservoir system ispreferred to eliminate air/blood interface and associated blood trauma.The venous blood exits the reservoir through tube 58 (e.g. ⅜inch ID PVCtubing). This tube is connected to an oxygenator/heat exchanger means 59(such as the COBE Cardiovascular, Inc. model #CML DUO #050-257-000) tooxygenate the oxygen-depleted blood. The blood will be pumped throughthe membrane/heat exchanger by a roller pump device 60 (such as the COBECardiovascular, Inc. model #043-600-000). The oxygenator will oxygenatethe blood and the heat exchanger will regulate blood temperature. Theoxygenated arterial blood will exit means 59 through tube 61 (such as⅜inch ID tubing), pass through an arterial filter 62 (such as a COBECardiovascular, Inc. Sentry #020-954-000) and be delivered into thefemoral artery via the invention multichannel catheter 63. Preferably,all blood contact components are surface modified to reduce bloodtrauma, patient inflammatory response and requirements for patientanticoagulation.

[0132] The invention femoral artery catheter 63 provides flow ofoxygenated blood to the aorta 64. The invention catheter 63 isintroduced into the femoral artery 65 percutaneously or by cut down. Theinvention catheter 63 is introduced utilizing a guidewire and stylet.The stylet provides stability to the catheter allowing the device toresist kinking during insertion with a minimum required wall thicknessof the catheter. Accurate positioning of the balloon will differ fromother positioning methods by utilizing measurement of the cardiac.catheterization catheter. The appropriate distance will be determinedand indicated on the femoral artery catheter 63 prior to insertion; thedistance indicator markings 66 will provide simple and accurate balloonpositioning. Accurate positioning of the balloon tip may also beenhanced or verified using visualization by transesophogial echo orfluoroscopy.

[0133] The invention catheter provides a flow of oxygenated blood to theaorta as part of the cardiopulmonary bypass process. The catheter is ofa length sufficient to extend from the insertion point in the femoralartery to the ascending aorta as shown in FIG. 11, which length willvary depending on the size of the patient, as discussed hereinbefore.The catheter has a proximal end 74 and a distal end 75. The catheter hasan inflatable balloon 76 located on the proximal side of the distal tipfor fixing the catheter within the ascending aorta. A channel extendsthe length of the catheter to the balloon with an outlet port thatcommunicates with the balloon so that the balloon can be filled with afluid from a syringe-type inflation device 73 to occlude the ascendingaorta as discussed herein. The catheter also has (a) a channel extendingfrom the proximal end 74 to outlet ports 77 upstream of the balloon fordelivering oxygenated blood and (b) a channel extending through theentire cannula with an outlet port 78 in the distal tip for a guidewireand/or delivering a cardioplegia solution to the heart through stopcock68 into inlet port 67 and line 69. Changing the position of the valve instopcock 68 to connect with line 70 and providing a negative pressure byroller pump 72, allows for the venting of the left ventricle by pullingfluid from the left ventricle through the semilunar valve throughopening 78.

[0134] Another aspect of this invention may be viewed as an improvementin the process of minimally or “least” invasive heart surgery. Fortraditional open heart surgery, the surgeon is required to make a longincision in the front of the chest and divide the sternum bone to gainaccess for the procedure. In minimally invasive heart surgery, a series(4-7) of small incisions are made and the operation is carried outthrough narrow tubes or ports, using direct or video assistedvisualization. Such a minimally invasive process and associatedtechniques are described in various aspects in U.S. Pat. No. 5,433,700;5,458,574; and 5,452,733, all of which are incorporated by reference intheir entirety.

[0135] Another aspect of this invention is the overall management ofcoronary artery disease management using the scheme outlined as follows,in which the multichannel catheter is used in the diagnostic evaluationand ensuing treatment, particularly the surgical treatment. Generally,the management is a combination of preventative care, treatment andfollow-up and can be diagrammed as follows:

[0136] How to make the Catheter

[0137] Generally the multichannel catheter of this invention is preparedusing any technique that provides the multichannel catheter hereindescribed. The key is to ensure that the second and third channels areintegrated into the wall of the first channel. This may be done byforming the channels separately then conjoining them, i.e. by gluing orother means. However, the multichannel catheter may be made through amandrel-dipping technique, or preferably a continuous extrusion process.Extrusion involves forcing a fluid polymer material (as discussed above)through a suitably-shaped die to produce the cross-sectional shape, suchas that depicted in FIGS. 5A, 5B, 5C and 6 or other suitable shape asdescribed herein. The extruding force may be exerted by any standardmeans known in the art such as by a piston or ram or by a rotatingscrew, which operates within a cylinder in which the polymeric materialsuch as PVC or polyurethane is heated and fluidized. The fluid materialis then extruded through the die in a continuous flow. The extrusionhead will have a multitubular die to provide a continuous multichannelcatheter, essentially as described herein. Using a mandrel- dippingtechnique, a mandrel having the desired size and cross section design isdipped in or drawn through a fluid polymeric material so that themandrel is coated with the polymer. The polymer is then dried on themandrel and removed to give the desired design. This technique may bedone at commercial manufacturers, e.g., PTG, Emeryville, California andothers.

[0138] Once the multichannel catheter is formed, whether by extrusion ormandrel- dipping, it is cut to suitable lengths and treated to providethe further characteristics of the product to make it operable. Suchtreatment may occur in any particular order. For example, a plurality ofopenings (40 in FIG. 4) are formed near the distal end of said cathetercommunicating with said first channel. These openings are made inconformance with the designs discussed herein, and thus are preferablyelongate in that the longitudinal axis of the elongate design may behelical or orthogonal, but is preferably substantially parallel to thelongitudinal axis of the catheter itself. The openings may be providedby suitably cutting or punching the elongate design into the wall of thecatheter. The design is approximately oval, rectangular, or the likewith the length of the opening being about a size discussed hereinbefore. The width of the opening will be such it will not weaken thestructural integrity of the distal end of the catheter. FIGS. 8, 9 and10 present various configurations for the positioning of openings 40.Optionally, additional openings communicating with the first channel maybe provided along the length of the catheter positioned betweenapproximately the middle of the catheter and the elongate openings nearthe distal end. The openings are useful in reducing the pressure dropbetween the proximal end of the catheter and the distal openings to helpreduce the sheer stress on the blood.

[0139] In addition to the openings that communicate with the first,large channel, at least one opening communicates with the third channel.Thereafter, an inflatable means, i.e. a balloon device, is integratedinto the distal end of the catheter such that the interior of theballoon communicates with the outlet of the third channel to allow fluidto flow through the third channel and to the interior of the inflatablemeans. In general, this may, be integrated by positioning a balloonhaving an opening corresponding to the opening to the third channel andadhering the balloon to the distal end of the catheter between theopenings to the first large channel of the catheter and the distal tipof the catheter. This adherence may be performed by using a suitableglue, solvent bond, light sensitive weld, or other suitable means knownin the art for this purpose. The material used for the inflatable meansmay be any suitable biocompatible material that is capable of beinginflated and deflated a plurality of times. Polyurethane-basedbiocompatible polymers are preferred. These are described in theaforementioned article by Ward, et al.

[0140] Finally, the distal end of the first, large channel and thethird, small channel are closed. This may be achieved by plugging,solvent sealing, heating or other suitable means. The process must becarried out in such a way that the distal end of the second channelremains open.

[0141] Having now described in detail how to make and use the catheterof this invention, the following non-limiting example is provided tofurther explain important concepts of the invention. The example is tobe interpreted as representative but not limiting the scope of coverageof this patent application.

[0142] All references to any patents or articles in this application areto be interpreted to specially incorporate each in this application byreference.

Example 1

[0143] This Example shows the importance of the second and thirdchannels, i.e., smaller channels 36 and 38 in the Figures, in themultichannel catheter bearing integrated into the wall of the largerchannel and the importance of a significant outflow capacity in theoutlet ports to minimize the pressure drop as the flow rate increasesthrough the large channel.

[0144] In this test ⅜″ inside diameter PVC tubing was used as a channelfor standard saline solution. The flow rate through the various tubeswas varied from 0.5 to 6 liters per minute. The saline was pumped from afirst canister to a second using a roller pump. Tubes 1-6 havingslightly different designs were used in the test as follows:

[0145] Tube #1: This had two tubes of a much smaller outside diameter,i.e., about ⅛″ and about {fraction (1/32)}″) within the length of largepassageway that were not integrate dinto the wall of the ⅜″ tube. It had3 circular outlets of about 2mm diameter at its distal end adjacent theballoon.

[0146] Tube #2: This was similar to #1 except it had 3 slightly largeroval outlets of about 2mm by about ¾″ in. (about 20mm) Tube #3: Samedesign as #2 with 5 additional circular distal outlets of about 2mmdiameter each.

[0147] Tube #4: Same design as #2 with 10 additional circular distaloutlets of about 2mm diameter each.

[0148] Tube #5: Same design as #2 with 15 additional circular distaloutlets of about 2mm diameter each.

[0149] Tube #6: Same design as #1 without the interior tubing.

[0150] The pressure drop was measured by pressure manometer gauge priorto the catheter. The saline was pumped through the catheter starting onthe proximal end and flowing out the distal end through the outletports. Table I shows the results of the test. It clearly shows theimportance of not having any interior lines that are not integrated intothe wall of the large catheter. The pressure drops at all flow rates aremuch less for design #6 (more than 50%). Also when the outflow capacityincreases the pressure drop decreases, thus placing less stress on thefluid. TABLE I Pressure Drop Flow #1 #2 #3 #4 #5 #6 Rate 0 0 0 0 0 0 .532 32 30 20 20 21 1 51 51 51 49 49 30 1.5 74 74 65 65 59 58 2 109 105 8989 84 42 2.5 148 140 120 120 110 49 3 195 190 158 158 147 62 3.5 250 238192 192 178 82 4 300 286 231 231 216 97 4.5 354 335 270 265 251 119 5450 430 380 370 350 148 6

The subject matter claimed is:
 1. A multichannel catheter having distaland proximal ends, which catheter comprises a central, first channel (i)extending substantially the length of the catheter, (ii) comprising atleast about seventy percent of the available channel volume of thecatheter, (iii) being defined by the wall of the catheter, and (iv)being closed at its distal end; a second channel (i) extendingsubstantially the length of the catheter parallel to said first channelbut independent thereof, (ii) being integrated into the wall of thefirst channel, and (iii) being open at its distal end; a third channel(i) extending substantially the length of said catheter parallel to saidfirst and second channels but independent thereof, (ii) comprising, incombination with the second channel, not more than about thirty percentof the available channel volume of the catheter, and (iii) beingintegrated into the wall of the first channel and spaced from the secondchannel; a plurality of openings in the wall of the catheter near thedistal end of said catheter and communicating only with said firstchannel; and an inflatable means integrated into the distal end of thecatheter between said first channel openings and said second channeldistal opening and with the distal opening of said third channel influid communication with the interior of the inflatable means, whereinthe catheter is of a size suitable for insertion into a blood vessel ofa mammal.
 2. The catheter of claim 1 wherein the outflow capacity of theplurality of openings communicating with said first channel exceeds theinflow capacity into the first channel.
 3. The catheter of claim 2wherein a majority of the plurality of openings are elongate with thelength of each elongate opening being parallel to the length of thecatheter.
 4. The catheter of claim 1 wherein the catheter is of a lengththat is sufficient to allow insertion into a femoral artery andpositioning such that the distal end of the catheter is located in theascending aorta such that the openings communicating with the firstchannel are positioned substantially adjacent the great arteries.
 5. Thecatheter of claim 1 wherein the catheter is made using an extrusiontechnique.
 6. The catheter of claim 1 wherein markings are positionednear the proximal end of the catheter to mark the distance from thedistal end of the catheter.
 7. A process of preparing a multichannelcatheter that is of a size suitable for insertion into a blood vessel ofa mammal, which process comprises (A) extrusion molding a catheterhaving distal and proximal ends wherein the catheter comprises (1) acentral, first channel (a) extending substantially the length of thecatheter, (b) comprising at least about seventy percent of the availablechannel volume of the catheter, and (c) being defined by the wall of thecatheter; (2) a second channel (a) extending substantially the length ofthe catheter parallel to said first channel but independent thereof and(b) being integrated into the wall of the first channel; (3) a thirdchannel (a) extending substantially the length of said catheter parallelto said first and second channels but independent thereof, (b)comprising, in combination with the second channel, not more than aboutthirty percent of the available channel volume of the catheter, and (c)being integrated into the wall of the first channel and spaced from saidsecond channel.
 8. The process of claim 7 that comprises in addition to:(A) forming a plurality of openings in the wall of the catheter near thedistal end of said catheter and communicating only with said firstchannel; (B) integrating an inflatable means into the distal end of thecatheter positioned distal to said first channel openings so that theinflatable interior of the means in fluid communication with said thirdchannel through an opening in the wall of the catheter, and (C) formingat least one opening positioned distal to the inflatable means andcommunicating with said second channel; (D) closing the distal end ofsaid first channel.
 9. The process of claim 8 wherein the outflowcapacity of said plurality of openings communicating with said firstchannel exceeds the inflow capacity of the first channel.
 10. Theprocess of claim 9 wherein a majority of the plurality of opening are,elongate with the length being parallel to the length of the catheter.11. The process of claim 8 wherein the catheter is of a length that issufficient to allow insertion into a femoral artery and positioning suchthat the distal end of the catheter may be located in the ascendingaorta such that the openings communicating with the first channel arepositioned substantially adjacent the great arteries.
 12. A process forproviding oxygen-rich blood to a patient's arterial circulation whileproviding a biologically active fluid to the heart of the subject, whichprocess comprises positioning a multichannel catheter having a proximalend and a distal end in the patient²s aorta, wherein said multichannelcatheter comprises (a) a central, first channel (i) extendingsubstantially the length of the catheter, (ii) comprising at least aboutseventy percent of the available channel volume of the catheter, (iii)being closed at the distal end of said catheter and (iv) being definedby the wall of the catheter; (b) a second channel (i) extendingsubstantially the length of the catheter parallel to said first channelbut independent thereof and (ii) being integrated into the wall of thefirst channel; (c) a third channel (i) extending substantially thelength of said catheter parallel to said first and second channels butindependent thereof, (ii) comprising, in combination with the secondchannel, not more than about thirty percent of the available channelvolume of the catheter, and (iii) being integrated into the wall of thefirst channel and spaced from said second channel; (d) a plurality ofopenings near the distal end of said catheter communication only withsaid first channel; (e) at least one opening at the distal end of thecatheter communicating with said second channel; (f) an inflatable means(i) integrated into the distal end of the catheter between said firstchannel openings and said second channel opening and (ii) communicatingwith said third channel through an opening in the wall of the catheter;providing a source of oxygen-rich blood to the proximal end of saidfirst channel; providing a source of biologically active fluid to theproximal end of said second channel; providing a source of fluid forinflating said inflatable means to the proximal end of said thirdchannel; positioning said multichannel catheter within the subject'sblood circulatory system such that the distal end of said catheter ispositioned in the ascending aorta so that the first channel openings arelocated upstream of the inflatable means, the inflatable means islocated on the cephalid side of the aortic valve and the distal end ofthe second channel is located downstream of the inflatable means andproximate the aortic valve; optionally inflating said inflatable meansto block the flow of blood to the heart; pumping biologically activefluid into the heart; pumping oxygen-rich blood through said firstchannel out the first channel openings at rate sufficient to maintainthe subject's metabolism and perfusion; optionally performingcardiovascular surgery on the heart as needed; and maintaining thecirculatory support for said subject as needed.
 13. The process of claim12, wherein the biologically active fluid is a cardioplegia solution andthe cardiovascular surgery is cardiac surgery.
 14. A process forperforming cardiobvascular surgery, which process comprises inserting atleast one cannula into the mammal's peripheral veins with positioning sothe distal open end of the cannula is adjacent the vena cava regions ofthe mammal's heart and the proximal end of the cannula is attached to acardiopulmonary machine through a pump wherein said cardiopulmonarymachine comprises a blood oxygenation means fluidly connected to saidpump, inserting a multichannel catheter having a proximal end and adistal end into a femoral artery, wherein said multichannel cathetercomprises (a) a central, first channel (i) extending substantially thelength of the catheter, (ii) comprising at least about seventy percentof the available channel volume of the catheter, (iii) being closed atthe distal end of said catheter and (iv) being defined by the wall ofthe catheter; (b) a second channel (i) extending substantially thelength of the catheter parallel to said first channel but independentthereof, and (ii) being integrated into the wall of the first channel;(c) a third channel (i) extending substantially the length of saidcatheter parallel to said first and second channels but independentthereof, (ii) comprising, in combination with the second channel, notmore than about thirty percent of the available channel volume of thecatheter, and (iii) being integrated into the wall of the first channeland spaced from said second channel; (d) a plurality of openings nearthe distal end of said catheter communication only with said firstchannel; (e) at least one opening at the distal end of the cathetercommunicating with said second channel; (f) an inflatable means (i)integrated into the distal end of the catheter between said firstchannel openings and said second channel opening and (ii) communicatingwith said third channel through an opening in the wall of the catheter;positioning said multichannel catheter within the subject's bloodcirculatory system such that the distal end of said catheter ispositioned in the ascending aorta such that the first channel openingsare located upstream of the inflatable means and proximate the greatarteries, said inflatable means is located on the cephalid side of theaortic valve and the distal end of the second channel is locateddownstream of the inflatable means and proximate the aortic valve;providing a source of oxygenated blood from the cardiopulmonary machineto the proximal end of said first channel; providing a source ofbiologically active fluid to the proximal end of said second channel;providing a source of fluid for inflating said inflatable means to theproximal end of said third channel; inflating said inflatable means toblock the flow of blood to the heart; optionally pumping cardioplegiasolution into the heart to arrest the mammal's heart; pumpingoxygen-rich blood through said first channel out the first channelopenings at rate sufficient to maintain the subject's metabolism andperfuision; removing oxygen depleted from the mammal's vena cavaeregions through the femoral vein cannula by applying a negative pressureusing the centrifugal pump; performing cardiovascular surgery as needed;and maintaining the circulatory support for said subject as needed. 15.A single multichannel catheter useful for extracorporeal circulation ofblood to a patient undergoing cardiovascular surgery wherein thecatheter comprises at least three independent channels and an expandableballoon at one end of the catheter, a first largest channel of a size toallow delivery of an amount of blood to the patient that is sufficientto support the patient metabolism and perfusion throughout the surgery,a second channel, smaller than the first channel and integrated into thewall of the first channel, said second channel suitable for (a)delivering cardioplegia solution to the heart and (b) venting the leftheart, and a third channel also smaller than the first channel andintegrated into the wall of the first channel said third channelsuitable for delivery of a fluid to the balloon for its expansion whenpositioned in the ascending aorta to occlude the flow of blood.
 16. Thecatheter of claim 15 of a length sufficient to be inserted throughout afemoral artery and positioned so that the balloon is positioned in theascending aorta.
 17. The catheter of claim 15 wherein the blood isdelivered to the patient through openings in the wall of the firstchannel that are upstream of the balloon and the cardioplegia solutionis delivered and the left heart is vented through an opening in thesecond channel that is downstream of the balloon.
 18. In a method forperforming cardiovascular surgery on a patient using acardiopulmonary-machine for extracorporeal circulation of blood, theimprovement that comprises using a single, multichannel catheter for theextracorporeal circulation wherein the multichannel catheter comprisesat least three independent channels and an expandable balloon at thedistal end of the catheter, a first largest channel of a size to allowdelivery of an amount of blood to the patient that is sufficient tosupport the patient metabolism and perfusion throughout the surgery, asecond channel, smaller than the first channel and integrated into thewall of the first channel, said second channel suitable for (a)delivering cardioplegia solution to the heart and (b) venting the leftheart, and a third channel also smaller than the first channel andintegrated into the wall of the first channels, said third channelsuitable for delivery of a fluid to the balloon for its expansion whenpositioned in the ascending aorta to occlude the flow of blood.
 19. Themethod of claim 18 wherein the blood is delivered to the patient throughopenings in the wall of the first channel that are upstream of theballoon and the cardioplegia solution is delivered through the secondchannel out an opening that is downstream of the balloon.
 20. The methodof claim 19 wherein the surgery is open-chest surgery and the catheteris inserted through the patient's aorta or one of the great arteries andpositioned so that the balloon in located in the ascending aorta toocclude the flow of blood to the heart.
 21. The method of claim 19wherein the surgery is minimally invasive surgery and the catheter isinserted into the patient through the patient's femoral artery andpositioned so that the balloon in located in the ascending aorta toocclude the flow of blood to the heart.
 22. A method of delivering abiologically active agent to a subject in need thereof, which methodcomprises administering the agent using the multichannel catheter ofclaim
 1. 23. The method of claim 21 wherein the agent is a cardioplegiasolution delivered through the second channel to the heart of a patientin need thereof.